April 22, 2014

Antarctica Was A Balmy 63 Degrees Fahrenheit During The Eocene

Previous studies have shown that Antarctica was a much warmer continent 40 to 50 million years ago and a new report from a team of American, Dutch and Australian researchers has revealed finer details on the milder temperature that blanketed the region at the time.

Published on Monday in the Proceedings of the National Academy of Sciences, the new report revealed that parts of Antarctica were as warm as Coastal California and sea temperature of the southern Pacific that are just above the freezing point today used to be about 72 degrees F during the Eocene epoch.

During the Eocene, around 40 to 50 million years ago, the Earth contained high levels of atmospheric carbon dioxide and as a result a greenhouse effect blanketed the world. With modern levels of carbon dioxide, the Earth has segmented into multiple climate zones, with Antarctica one of the coldest places on Earth year-round.

The study team said their research could be used to develop climate models for future elevated levels of atmospheric carbon dioxide.

"Quantifying past temperatures helps us understand the sensitivity of the climate system to greenhouse gases, and especially the amplification of global warming in polar regions," said study author Hagit Affek, an associate professor of geology and geophysics at Yale University.

To reach their findings, the researchers assessed levels of uncommon isotopes in fossilized sea shells collected at Seymour Island, an island near the northeast side of the Antarctic Peninsula. The shells were analyzed using a method called carbonate clumped isotope thermometry.

The researchers discovered that temperatures in areas of Antarctica reached as high as 63 degrees F during the Eocene, with an average of 57 degrees F – comparable to the yearly average off the modern-day coast of California. They also found temperatures for the southern Pacific Ocean that resembled seawater temperatures near modern-day Florida.

The study team also found that Eocene ocean temperatures were not evenly spread throughout the Antarctic ocean regions — they were warmer on the South Pacific side of Antarctica — suggesting that ocean currents led to a temperature difference.

"By measuring past temperatures in different parts of Antarctica, this study gives us a clearer perspective of just how warm Antarctica was when the Earth's atmosphere contained much more CO2 than it does today," said study author Peter M.J. Douglas, a postdoctoral scholar at the California Institute of Technology. "We now know that it was warm across the continent, but also that some parts were considerably warmer than others. This provides strong evidence that global warming is especially pronounced close to the Earth's poles.”

“Warming in these regions has significant consequences for climate well beyond the high latitudes due to ocean circulation and melting of polar ice that leads to sea level rise,” he added.

"We managed to combine data from a variety of geochemical techniques on past environmental conditions with climate model simulations to learn something new about how the Earth's climate system works under conditions different from its current state," Affek said. "This combined result provides a fuller picture than either approach could on its own."